Couple Questions about A/F Ratio's

[cmptrphreak]

Alright, So I am tuning my car with a maft with a blow through setup. I am using the stock o2 sensor to tune the car and a TMO data logger. When I drive the car normally with minimal boost(Regular driving). In the first the a/f ratio shoots to 20.0 and then goes back to 14.7 ish . I know 14.7 is the stoichiometric ratio for cruise. Im shooting for a 11.1 - 11.5 ratio which I do have. So should the ratio shoot to 20.0 at all? Also sometimes at idle the ratio might go up to 17 and then go back to 14.7 .

[Talonguy5]

The narrowband O2 sensor (stock) is useless for tuning WOT. It is not anywhere NEAR accurate enough to use it for what you're trying to do.

Either use a wideband, or tune by watching knocksum.

[turboglenn]

Where does it shoot to 20? WOT idle? If you can be more descriptive about what happens and when you will get more help. Your question is too vague for any answers other than not to use a narrowband 02 and to also let you know a MAFT is not enough to really "tune" with, it simply allows a different MAF meter to be installed and calibrated. trying to tune with the MAFT will allow one area to be correct while everythign else will be rough at best

[cmptrphreak]

At idle the A/F Ratio shoots from 14.7 to 20 and sits and 14.7 and will go back to 20 every so often. I dont touch the accelerator peddle at that time. The other thing is when just going in 1st like the rpms are going from 850 to 3000 and the car is moving the a/f ratio sits at 20. Even If I gun the hell out it it will do it but in second the ratio goes down to 11.1 when i gun it in wot and 14.7 when im just driving normally.

[turboglenn]

Well, that all sounds like you're too lean in those areas, but i t could be just another crappy narrow band 02 fluctuating all over the place while the actual AFR is only moving by a half to one point.

The car randomly going to 20:1 and then back to 14 sounds like it' s having to make too much correction to the fuel trims in one direction and then while it's in one extreme end of correction the map moves into a cell that doens't need nearly as much and the AFR flies off to one end untill the closed loop corrects again